Quartile field, need to change. Is this possible?

I have a request to change the computation for the quartile field. This field is visible on the salary screen, is titled quartile and has a range of 1-4 based on how the participate falls in the grade range. My compensation team wants to change this to a range of 1-3, more of a thirds kind of rating. Is this possible?

Thanks in advance for any guidance.

Dawn